Expression that defines a relationship of direct variation.
A relationship of direct variation is defined by a rule in the form y = kx where k is a constant.
Example
This graph illustrates the function f defined by f(x) = –2x. In this case, the constant k is –2.
We can also represent a linear relationship using a table of values:
| -5 | -2 | 0 | 1 | 3 | |
| 10 | 4 | 0 | -2 | -6 |